Development inhibitor releasing compounds or couplers (DIR's) are compounds that release development inhibitor compounds upon reaction with oxidized developer. DIR's are used in photographic materials to improve image sharpness (actance), reduce gamma-normalized granularity (a measure of signal to noise ratio with a low gamma-normalized granularity indicating a beneficial high signal to noise ratio), control tone scale, and control color correction.
It is often desirable to maximize the amount of development inhibitor that is released in order to maximize the amount of sharpness and minimize the contrast(gamma)-normalized granularity of the image produced in a photographic material. However, the amount of tone scale control and color correction control must usually be maintained within specific limits for visually pleasing image reproduction. This often limits the degree of sharpness and gamma-normalized granularity improvement that can be obtained through the use of DIR compounds.
This problem has been addressed in a number of ways. One way to increase image sharpness provided by a DIR compound is to increase the effective mobility of the released inhibitor compound by linking it to a coupler moiety through a timing group. Upon reaction with oxidized developer, the timing-inhibitor moiety is cleaved from the coupler moiety. The inhibitor moiety releases from the timing group and thus becomes active, but only after a delay during which the timing-inhibitor moiety could move in the material. The incorporation of such timing groups in DIR's and the advantages thereby achieved are described in, for example, U.S. Pat. Nos. 4,284,962 and 4,409,323. An example of such a timed DIR is: ##STR1##
These compounds may provide undesirably high levels of color correction. A technique to control the amount of color correction, the so-called interimage effect, utilizes a DIR that releases an inhibitor moiety that comprises a ballasting group --Q enabling, upon exposure and processing of the material, reduced interlayer interimage effect without reduced image acutance. Such DIR's are described in the U.S. patent application Ser. No. 366,730 filed Jun. 15, 1989, now U.S. Pat. No. 5,006,448. These DIR's, however, do not provide both the high photographic speed and the reductions in gamma-normalized granularity to the extent that is often desirable.
It would therefore be highly desirable to provide a photographic material that offered the concomitant advantages of high image sharpness, low interlayer interimage effect, high photographic speed and low gamma-normalized granularity.
In an unrelated area, it has been taught to incorporate bleach accelerator-releasing compounds (BARC's) in photographic materials to aid in the bleaching step of photographic processing. European Patent Application Publication No. 193,389 discloses BARC's having a releasable thioether bonded to an alkylene group or heterocyclic nucleus with a solubilizing group attached thereto. One such BARC, having the formula: ##STR2## has been used as such in a color negative film, which also contained the above-identified DIR-1. This DIR does not have a --Q ballasting group. This combination, as shown below by comparative data, did not provide both high photographic speed and as great a reduction in gamma-normalized granularity as might be desired.
European Patent Applications 169,458 and 272,573 and German OLS 3,626,219, 3,636,824, 3,644,405 and 3,644,416 disclose photographic elements comprising couplers which release monocyclic triazole development inhibitor moieties, several of which are substituted with thioalkyl moieties. The photographic elements of these applications are described as exhibiting large interimage effects. No mention is made of BARC couplers in these applications.
U.S. Pat. No. 4,791,049 discloses photographic elements comprising inhibitor releasing developers which release thiadiazole development inhibitor moieties, several of which are substituted with thioalkyl moieties. The photographic elements of this application are described as exhibiting large interimage effects. No mention is made of BARC couplers in this application.